The present invention relates to an improved crystal oscillator circuit, and more particularly to an ultra low noise oscillator circuit. Previously, low noise oscillator circuits could provide -135 dbc in a 1 Hz bandwidth at 100 Hz offset from carrier. However, current communications and radar systems require signal sources that have greater spectral purity (e.g., lower phase noise) than previously obtainable. For example, in current radar systems noise in the radar signal source causes the position of targets to be blurred. One result of such blurring is that smaller adjacent targets appear as one, or are obliterated by a larger target due to the jittering of the target return (i.e. phase noise in the radar oscillator).